r5102: This is a major simplification of the logic for controlling top level

r5102: This is a major simplification of the logic for controlling top level
servers in smbd. The old code still contained a fairly bit of legacy
from the time when smbd was only handling SMB connection. The new code
gets rid of all of the smb_server specific code in smbd/, and creates
a much simpler infrastructures for new server code.

Major changes include:

 - simplified the process model code a lot.

 - got rid of the top level server and service structures
   completely. The top level context is now the event_context. This
   got rid of service.h and server.h completely (they were the most
   confusing parts of the old code)

 - added service_stream.[ch] for the helper functions that are
   specific to stream type services (services that handle streams, and
   use a logically separate process per connection)

 - got rid of the builtin idle_handler code in the service logic, as
   none of the servers were using it, and it can easily be handled by
   a server in future by adding its own timed_event to the event
   context.

 - fixed some major memory leaks in the rpc server code.

 - added registration of servers, rather than hard coding our list of
   possible servers. This allows for servers as modules in the future.

 - temporarily disabled the winbind code until I add the helper
   functions for that type of server

 - added error checking on service startup. If a configured server
   fails to startup then smbd doesn't startup.

 - cleaned up the command line handling in smbd, removing unused options